Explanation​:
There is no polyatomic ion with the formula of CO4 ^2−​. The correct formula for the carbonate ion is CO3^2−​. The formulas and charges of the other ions are correct.

Explanation​:
Strontium is in group 2 and so forms Sr2+ ions. The formula of the sulfide ion is S2− as sulfur is in group 16. For the positive and negative charges to cancel out, one of each ion is required.

Explanation:​
There are three bonding pairs and no lone pairs around the central B atom giving it a trigonal planar shape. As this is symmetrical, there is no net dipole even though the individual bonds are polar. There are only six electrons around the central B atom making it electron deficient (it has not achieved its octet).

Explanation​:
Carboxylic acids have hydrogen bonding due to O−H bonds.

Explanation:​
Alloys are homogeneous mixtures of metals with other metals or nonmetals.

Explanation​:
All statements are correct, but only D is a reason for solubility in water

Explanation​:
Oxidation reaction; Magnesium is much less electronegative than oxygen, so the Mg atoms lose electrons to the O atoms during the reaction. This process forms positive Mg2+ ions, termed cations, and negative O2− ions, termed anions.

This question is categorized as easy, as the student must recall two pieces of information that are covered extensively in the syllabus.

Explanation​:
Volatility refers to the ease at which a substance vaporizes. Ionic bonds are very strong and, therefore, a lot of energy is required to turn ionic compounds into gases.

Polar solvents are able to form electrostatic forces of attraction with ions.

Explanation:​
Triple bonds are stronger than double bonds which are in turn stronger than single bonds. The greater the number of shared pairs of electrons, the stronger the bond and the greater the bond enthalpy.

Explanation​:
There is no polyatomic ion with the formula of CO42−COX42−​. The correct formula for the carbonate ion is CO32−COX32−​. The formulas and charges of the other ions are correct.

Explanation:​
C3H6​ belongs to the alkene class with the general formula CnH2n​, and has a three carbon chain.

Explanation:
Non-metal elements bond to each other covalently. Ca3N2​ is made up of a metal and a nonmetal (with a large difference in electronegativity) and has ionic bonding.

Explanation:​
The central atom is carbon with two C-H single bonds and one C=O bond. This gives 3 electron domains and 8 valence electrons.

Explanation:
Non-metal elements bond to each other covalently. Ca3N2​ is made up of a metal and a nonmetal (with a large difference in electronegativity) and has ionic bonding.

Explanation:
The higher the charge of the ions, the stronger the electrostatic forces of attraction and, therefore, the greater the lattice enthalpy.
The smaller the ion, the greater the charge density and the stronger the electrostatic attraction between oppositely charged ions.
Statement I is incorrect since the smaller the lattice enthalpy, the weaker the electrostatic attraction and the lower the melting point is.

Explanation:​
Metals characteristically have high melting points due to strong metallic bonds.

Explanation:
Non-metal elements bond to each other covalently. Ca3N2​ is made up of a metal and a nonmetal (with a large difference in electronegativity) and has ionic bonding.

Explanation:​
Recall of description of metallic bonding as positive ions surrounded by delocalized electrons.

Explanation​:
Recall that hydrogen bonds are the strongest intermolecular forces, and London forces are the weakest.

Explanation​:
Choice A refers to ionic bonding;
Choice B could refer to ionic bonding or specifically coordinate (dative) bonding;
Choice C refers to hydrogen bonding.

Explanation:
Oppositely charged ions attract, it is an ionic bonding;

Choice A describes metallic bonding;

Choice B describes a simple molecular lattice;

Choice D describes a covalent bond.

Explanation:​
To answer this question, the student must apply the data to the van Arkel-Ketelaar triangle to determine the type of bonding present in the molecule.

The bonding triangle analysis shows that the material is an ionic compound. Therefore, characteristic properties include that it is a crystalline lattice with a high melting point.

This question is categorized as easy since the student only needs to apply the data to Section 17 of the data booklet and then recall the basic properties of matter.

Explanation​:
Magnesium has two electrons in its outermost shell and loses both to achieve a full outer shell (Mg^2+). Fluorine has seven electrons in its outermost shell; it needs one more electron to achieve a full outer shell (F^1−).

Two fluorine atoms are therefore required for each magnesium atom in order to form a neutral ionic compound (where the charges of the positive and negative ions cancel out).